As the separation and recovery method of carbon dioxide, an absorption method, an adsorption method, a membrane separation method and the like are known.
Each of these methods has characteristics, advantages and disadvantages and thus is selected in accordance with the conditions in actual use. The absorption method is a method to separate carbon dioxide by dissolving an absorbent such as an amine alkali metal salt in water and is currently applied to thermal power plants, steel mills and the like in many cases. However, the absorption method has a number of problems such as excessive energy consumption for regeneration of the absorbing liquid, the overflow and channeling phenomenon of absorbing liquid in the absorption tower, a small gas-liquid contact area, and corrosion of the absorbing liquid. The adsorption method is a method to adsorb the gas to be separated while allowing the mixed gas to pass through the bed filled with an adsorbent such as zeolite and has been applied to some gas treatment processes along with the study on various adsorbents, but the adsorption method has disadvantages that the use of a powdery adsorbent is limited due to the scattering problem and thus a granular adsorbent is used to have a decrease in contact efficiency, the flow velocity of the mixed gas in the bed is fast in the center and slow on the periphery and thus the adsorption mainly proceeds in the center to have a limited adsorption amount as compared to the amount of the adsorbent used, and it takes a long time to regenerate the adsorbent. The membrane separation method is a separation method that utilizes a hollow fiber membrane capable of selectively permeating a portion of the mixed gas and has disadvantages that it takes an excessively long time and excessive energy is consumed to separate the gas since the membrane permeation speed of the gas is slow and a high pressure is required to be applied.